B cell biology

Published on September 30, 2020   26 min

Other Talks in the Series: The Immune System - Key Concepts and Questions

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Hello. I'm Richard Cornall. I'm the Nuffield Professor of Clinical Medicine at the University of Oxford, and I'm going to talk to you today about B-cell biology.
A good place to start is an overview of the function of B-cells, which are called B-cells because they were discovered in the bursa of Fabricius in poultry. B-cells are characterised, of course, by a B-cell receptor, which doesn't itself signal but is associated with Ig-alpha and -beta chains which contain immunoreceptor tyrosine-based activation motifs, also known as ITAMs. I'm not going to discuss the actual signaling mechanisms in detail here today. The mode of B-cell activation is actually quite controversial, at least in vitro activation is by cross-linking and increasing the density of kinases relative to phosphatases. But in vivo, most B-cells, it's now appreciated, encounter antigen probably on the surface of other cells, and how that operates at low density is not entirely known. We look at the individual functions of B-cells. The most well known is, of course, antibody secretion, and this arises through B-cells being activated and then differentiating into plasma cells which secrete antibody either on the short-term or over long-term in the bone marrow. The second function of B-cells is to bind antigen through the B-cell receptor and present them on MHC class II receptors to activate the T-cell and obtain T-cell help. Third function, which has been appreciated more recently is to transport antigen within lymph nodes and the spleen particularly notably on complement receptors. The fourth function of B-cells is to secrete cytokines. In particular, some B-cells secrete IL-10, and these cells are defined by some groups as being regulatory B-cells. But unlike regulatory T-cells, there's no transcription factor that has been identified to define them as a unique subset. These functions may be overlapping with other activatory functions of B-cells and the plasticity of the B-cell subsets is not as yet clearly defined.